The limits of human performance

2008 ◽  
Vol 44 ◽  
pp. 11-26 ◽  
Author(s):  
Ralph Beneke ◽  
Dieter Böning
Keyword(s):  
Human Performance ◽  
Safety Margin ◽  
Afferent Input ◽  
Metabolic Energy ◽  
Human Organism ◽  
Mechanical Resistance ◽  
As Doping ◽  
Gene And Protein Expression ◽  
Underlying Mechanisms ◽  
Biochemical Research

Human performance, defined by mechanical resistance and distance per time, includes human, task and environmental factors, all interrelated. It requires metabolic energy provided by anaerobic and aerobic metabolic energy sources. These sources have specific limitations in the capacity and rate to provide re-phosphorylation energy, which determines individual ratios of aerobic and anaerobic metabolic power and their sustainability. In healthy athletes, limits to provide and utilize metabolic energy are multifactorial, carefully matched and include a safety margin imposed in order to protect the integrity of the human organism under maximal effort. Perception of afferent input associated with effort leads to conscious or unconscious decisions to modulate or terminate performance; however, the underlying mechanisms of cerebral control are not fully understood. The idea to move borders of performance with the help of biochemicals is two millennia old. Biochemical findings resulted in highly effective substances widely used to increase performance in daily life, during preparation for sport events and during competition, but many of them must be considered as doping and therefore illegal. Supplements and food have ergogenic potential; however, numerous concepts are controversially discussed with respect to legality and particularly evidence in terms of usefulness and risks. The effect of evidence-based nutritional strategies on adaptations in terms of gene and protein expression that occur in skeletal muscle during and after exercise training sessions is widely unknown. Biochemical research is essential for better understanding of the basic mechanisms causing fatigue and the regulation of the dynamic adaptation to physical and mental training.

Exercise Physiology From 1980 to 2020: Application of the Natural Sciences

2021 ◽  
pp. 1-10
Author(s):  
Jane A. Kent ◽  
Kate L. Hayes
Keyword(s):  
Human Performance ◽  
Exercise Physiology ◽  
Natural Sciences ◽  
The Past ◽  
Interdisciplinary Field ◽  
Advanced Technologies ◽  
Health And Disease ◽  
Fundamental Research ◽  
Research Questions ◽  
Underlying Mechanisms

The field of exercise physiology has enjoyed tremendous growth in the past 40 years. With its foundations in the natural sciences, it is an interdisciplinary field that is highly relevant to human performance and health. The focus of this review is on highlighting new approaches, knowledge, and opportunities that have emerged in exercise physiology over the last four decades. Key among these is the adoption of advanced technologies by exercise physiologists to address fundamental research questions, and the expansion of research topics to range from molecular to organismal, and population scales in order to clarify the underlying mechanisms and impact of physiological responses to exercise in health and disease. Collectively, these advances have ensured the position of the field as a partner in generating new knowledge across many scientific and health disciplines.

Abstract W MP87: PDGF Contributes to BMSC Treatment Induced Neurogenesis and White Matter and Axonal Remodeling in T2DM Stroke Rats

Stroke ◽  
2015 ◽  
Vol 46 (suppl_1) ◽  
Author(s):  
Alex Zacharek ◽  
Tao Yan ◽  
Michael Chopp` ◽  
Poornima Venkat ◽  
Ruizhou Ning ◽  
...  
Keyword(s):  
Cell Migration ◽  
White Matter ◽  
Artery Occlusion ◽  
Border Zone ◽  
Axonal Outgrowth ◽  
Ischemic Brain ◽  
Neuroblast Migration ◽  
Gene And Protein Expression ◽  
Underlying Mechanisms

Objective: Our previous studies have found that bone-marrow-stromal cell (BMSC) treatment of stroke in Type two DM (T2DM) rats, initiated at 3 days after stroke, improved functional recovery. Neurogenesis and white matter (WM) remodeling play an important role in neurorestorative effects after stroke. In this study, we tested whether BMSCs regulate neurogenesis and WM remodeling and the underlying mechanisms of BMSC induced neurorestorative effects in T2DM stroke rats. Methods: T2DM was induced with streptozotocin injection in addition to a high fat diet. T2DM rats were subjected to 2h of middle cerebral artery occlusion (MCAo), then treated with human BMSCs (5X106) or vehicle control (n=8/group) initiated at 3 days after MCAo and rats were monitored for 28 days. Neuroblast migration, WM changes, and gene and protein expression were measured in the ischemic brain. Subventricular zone (SVZ) explant cell migration and primary cortical neuron (PCN) axonal outgrowth measurements were performed in vitro. Results: BMSC treatment in T2DM rats significantly improves functional outcome and increases WM remodeling identified by increased myelin and axonal density. BMSCs also increase the neuroblast migration protein doublecortin (DCX, 25.0±4.3% vs control: 4.5±1.1%), platelet-derived growth factor (PDGF)-AA, and bFGF expression in the ischemic border zone. Angiogenic ELISA array data are consistent with the immunostaining data, showing that BMSC treatment increases PDGF-AA (2.1 fold), PDGF-BB (2.5 fold) and bFGF (1.8 fold) in the ischemic brain. Using an in vitro cell culture model, we found that BMSCs secrete high levels of PDGF. PDGF treatment significantly increases SVZ explant cell migration (1.7 fold) and PCN axonal outgrowth (1.9 fold) compared to non-treatment control. Inhibition of PDGF with neutralized anti-PDGF antibody significantly attenuates BMSC conditioned medium induced SVZ cell migration and PCN axon outgrowth. Conclusion: BMSC treatment of stroke in T2DM increases WM remodeling and neurogenesis as well as increases PDGF expression. PDGF not only promotes neuronal migration, but also increases axonal outgrowth. Therefore, increasing PDGF likely contributes to BMSC induced neurogenesis and WM remodeling in T2DM stroke rats.

Long-term effects of early pain and injury

2021 ◽  
pp. 21-37
Author(s):  
Orla Moriarty ◽  
Suellen M. Walker
Keyword(s):  
Nervous System ◽  
Early Life ◽  
Tissue Injury ◽  
Afferent Input ◽  
Laboratory Studies ◽  
Long Term Effects ◽  
Nociceptive Pathways ◽  
Noxious Stimuli ◽  
Underlying Mechanisms

Nociceptive pathways are functional following birth, and acute responses to noxious stimuli have been documented from early in development in clinical and laboratory studies. The ability of noxious afferent input to alter the level of sensitivity of nociceptive pathways in the adult nervous system, with, for example, the development of central sensitization, is well established. However, the developing nervous system has additional susceptibilities to alterations in neural activity, and pain in early life may produce effects not seen following the same input at older ages. As a result, early tissue injury may lead to persistent changes in somatosensory processing and altered sensitivity to future noxious stimuli. Furthermore, there is increasing evidence that neonatal pain can result in long-term changes in cognitive and affective behavior. Effects of pain in early life are superimposed on a highly plastic developing system, and long-term outcomes vary depending on the type and severity of the injury, and on the evaluation methods used. Laboratory studies allow evaluation of different injuries, potential confounding factors, underlying mechanisms, and potential analgesic modulation.

Long-term effects of early pain and injury: animal models

2013 ◽  
pp. 20-29 ◽  
Author(s):  
Suellen M. Walker
Keyword(s):  
Nervous System ◽  
Tissue Injury ◽  
Afferent Input ◽  
Somatosensory Processing ◽  
Laboratory Studies ◽  
Long Term Effects ◽  
Nociceptive Pathways ◽  
Acute Responses ◽  
Noxious Stimuli ◽  
Underlying Mechanisms

Nociceptive pathways are functional following birth and acute responses to noxious stimuli have been documented from early development in both clinical and laboratory studies. The ability of noxious afferent input to alter the level of sensitivity of nociceptive pathways in the adult nervous system, with, for example the development of central sensitization, is well established (Woolf, 2011). However, the developing nervous system has additional susceptibilities to alterations in neural activity, and increases due to pain and injury in early life may produce effects not seen following the same input at older ages. As a result, early tissue injury may lead to persistent changes in somatosensory processing and altered sensitivity to future noxious stimuli. The impact of early pain and injury cannot be simply viewed as increasing or decreasing sensitivity as results vary depending on the type and severity of injury and the outcomes used for assessment. Laboratory studies allow evaluation of different forms of injury, potential confounding factors, underlying mechanisms, and potential for modulation by analgesia.

Methylphenidate causes cytotoxicity on photoreceptor cells via autophagy

2020 ◽  
Vol 40 (1) ◽  
pp. 71-80
Author(s):  
N Kong ◽  
Y Bao ◽  
H Zhao ◽  
X Kang ◽  
X Tai ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Protein Expression ◽  
Messenger Rna ◽  
Cell Damage ◽  
Photoreceptor Cells ◽  
Cell Toxicity ◽  
Hyperactivity Disorder ◽  
Increased Risk ◽  
Gene And Protein Expression ◽  
Underlying Mechanisms

Methylphenidate (MPH) is used as the first-line treatment for attention-deficit hyperactivity disorder. However, there are concerns that this treatment may be associated with increased risk of retinal damage. This study was to investigate cytotoxicity of MPH on photoreceptor cells and explore its underlying mechanisms. MPH-caused cell toxicity was established in 661 W cells. Cytotoxicity was evaluated by 3-(4,5-dimethylthiazol)-2,5-diphenyltetrazolium-bromid and lactate dehydrogenase assays. Oxidative stress was measured by the markers: glutathione (GSH) reductase, catalase, and superoxide dismutase activities as well as GSH, reactive oxygen species, and malondialdehyde levels. Gene and protein expression was detected by real-time polymerase chain reaction (PCR) and western blot, respectively. Results showed that MPH decreased 661 W cell viability, increased caspase-3/9 activities, and induced oxidative stress. Furthermore, MPH treatment increased messenger RNA (mRNA) expression of Beclin-1 and microtubule-associated protein 1A/1B-light chain 3B (LC3B) protein expression in 661 W cells, suggesting autophagy was induced. MPH treatment also upregulated p-JAK1/p-STAT1 protein expression. These data demonstrated that MPH could increase oxidative stress in photoreceptor cells to cause cell toxicity via autophagy, providing the scientific rationale for the photoreceptor cell damage caused by the MPH administration.

Modeling and Optimal Control of an Energy-Storing Prosthetic Knee

2012 ◽  
Vol 134 (5) ◽  
Author(s):  
Antonie J. van den Bogert ◽  
Sergey Samorezov ◽  
Brian L. Davis ◽  
William A. Smith
Keyword(s):  
Optimal Control ◽  
Energy Cost ◽  
Human Performance ◽  
Human Subjects ◽  
Metabolic Energy ◽  
Hydraulic Actuator ◽  
Joint Power ◽  
Storage Mechanism ◽  
Prosthetic Knee ◽  
Normal Knee

Advanced prosthetic knees for transfemoral amputees are currently based on controlled damper mechanisms. Such devices require little energy to operate, but can only produce negative or zero joint power, while normal knee joint function requires alternative phases of positive and negative work. The inability to generate positive work may limit the user’s functional capabilities, may cause undesirable adaptive behavior, and may contribute to excessive metabolic energy cost for locomotion. In order to overcome these problems, we present a novel concept for an energy-storing prosthetic knee, consisting of a rotary hydraulic actuator, two valves, and a spring-loaded hydraulic accumulator. In this paper, performance of the proposed device will be assessed by computational modeling and by simulation of functional activities. A computational model of the hydraulic system was developed, with methods to obtain optimal valve control patterns for any given activity. The objective function for optimal control was based on tracking of joint angles, tracking of joint moments, and the energy cost of operating the valves. Optimal control solutions were obtained, based on data collected from three subjects during walking, running, and a sit-stand-sit cycle. Optimal control simulations showed that the proposed device allows near-normal knee function during all three activities, provided that the accumulator stiffness was tuned to each activity. When the energy storage mechanism was turned off in the simulations, the system functioned as a controlled damper device and optimal control results were similar to literature data on human performance with such devices. When the accumulator stiffness was tuned to walking, simulated performance for the other activities was sub-optimal but still better than with a controlled damper. We conclude that the energy-storing knee concept is valid for the three activities studied, that modeling and optimal control can assist the design process, and that further studies using human subjects are justified.

scholarly journals Optimization of the Odor Microclimate

10.14311/324 ◽  
2002 ◽  
Vol 42 (2) ◽  
Author(s):  
M. V. Jokl
Keyword(s):  
Building Materials ◽  
Human Performance ◽  
Positive Impact ◽  
Performance Criteria ◽  
Human Organism ◽  
Air Filtration ◽  
Exhaust Fumes ◽  
Odor Removal ◽  
Building Ventilation ◽  
High Level

The odor microclimate is formed by gaseous airborne components perceived either as an unpleasant smell or as a pleasant smell. Smells enter the building interior partly from outdoors (exhaust fumes - flower fragrance) and partly from indoors (building materials, smoking cigarettes - cosmetics, dishes). They affect the human organism through the olfactory center which is connected to the part of brain that is responsible for controlling people's emotions and sexual feelings: smells therefore participate to a high level in mood formation. Sweet smells have a positive impact on human feelings and on human performance. Criteria for odor microclimate appraisal are presented together with ways of improving the odor microclimate (by stopping odors from spreading within a building, ventilation, air filtration, odor removal by plants, deodorization, etc.), including so-called AIR DESIGN.

scholarly journals Dihydrotestosterone induces pro-angiogenic factors and assists homing of MSC into the cardiac tissue

2018 ◽  
Vol 60 (1) ◽  
pp. 1-15 ◽  
Author(s):  
Mirel-Adrian Popa ◽  
Maria-Cristina Mihai ◽  
Alina Constantin ◽  
Viorel Şuică ◽  
Cătălin Ţucureanu ◽  
...  
Keyword(s):  
Cardiac Tissue ◽  
Immunohistochemical Analysis ◽  
Therapeutic Tool ◽  
Tissue Slices ◽  
Impedance Measurements ◽  
Qrt Pcr ◽  
Gene And Protein Expression ◽  
Underlying Mechanisms

The use of mesenchymal stem cells (MSC) as a therapeutic tool in cardiovascular diseases is promising. Since androgens exert some beneficial actions on the cardiovascular system, we tested our hypothesis that this hormone could promote MSC-mediated repair processes, also. Cultured MSCs isolated from Wharton’s jelly were exposed to 30 nM dihydrotestosterone (DHT) for 1 or 4 days and the effects of the hormone on their growth/migration/adhesion and the underlying mechanisms were assessed. Results were obtained by real-time cell impedance measurements, and DNA quantification showed that DHT increased MSC proliferation by ~30%. As determined by xCELLigence system, DHT augmented (~2 folds) the migration of MSC toward cardiac tissue slices (at 12 h), and this effect was blocked by flutamide, an androgen receptor (AR) antagonist. Exposure of cells to DHT, upregulated the gene and protein expression of AR, EMMPRIN and MMP-9 and downregulated the expression of MMP-2. DHT significantly induced the release of nitric oxide by MSC (≥2-fold) and flutamide blocked this effect. When MSCs were co-cultured with cardiac slices, immunohistochemical analysis and qRT-PCR showed that the integration of DHT-stimulated MSC was significantly higher than that of in controls. In conclusion, our findings provide the first evidence that DHT promotes MSC growth, migration and integration into the cardiac slices. The modulating effects of DHT were associated with upregulation of ARs and of key molecules known to promote tissue remodeling and angiogenesis. Our findings suggest that priming of MSC with DHT may potentially increase their capability to regenerate cardiac tissue; in vivo studies are needed to confirm our in vitro findings.

scholarly journals Musculoskeletal Model Personalization Affects Metabolic Cost Estimates for Walking

2020 ◽  
Author(s):  
Marleny Arones ◽  
Mohammad Shourijeh ◽  
Carolynn Patten ◽  
Benjamin J. Fregly
Keyword(s):  
Human Performance ◽  
Metabolic Cost ◽  
Musculoskeletal Model ◽  
Metabolic Energy ◽  
Cost Models ◽  
Cost Of Transport ◽  
Static Optimization ◽  
Musculoskeletal Models ◽  
Muscle Activations ◽  
Model Personalization

AbstractAssessment of metabolic energy cost as a metric for human performance has expanded across various fields within the scientific, clinical, and engineering communities. As an alternative to measuring metabolic cost experimentally, musculoskeletal models incorporating metabolic cost models have been developed. However, to utilize these models for practical applications, the accuracy of their metabolic cost predictions requires improvement. Previous studies have reported the benefits of using personalized musculoskeletal models for various applications, yet no study has evaluated how model personalization affects metabolic cost estimation. This study investigated the effect of musculoskeletal model personalization on estimates of metabolic cost of transport (CoT) during post-stroke walking using three commonly used metabolic cost models. We analyzed data previously collected from two male stroke survivors with right-sided hemiparesis. The three metabolic cost models were implemented within three musculoskeletal modeling approaches involving different levels of personalization. The first approach used a scaled generic OpenSim model and found muscle activations via static optimization (SOGen). The second approach used a personalized EMG-driven musculoskeletal model with personalized functional axes but found muscle activations via static optimization (SOCal). The third approach used the same personalized EMG-driven model but calculated muscle activations directly from EMG data (EMGCal). For each approach, the muscle activation estimates were used to calculate each subject’s cost of transport (CoT) at different gait speeds using three metabolic cost models (Umberger 2003, Umberger 2010, and Bhargava 2004). The calculated CoT values were compared with published CoT trends as a function of stance time, double support time, step positions, walking speed, and severity of motor impairment (i.e., Fugl-Meyer score). Overall, U10-SOCal, U10-EMGCal, U03-SOCal, and U03-EMGCal were able to produce slopes between CoT and the different measures of walking asymmetry that were statistically similar to those found in the literature. Although model personalization seemed to improve CoT estimates, further tuning of parameters associated with the different metabolic cost models in future studies may allow for realistic CoT predictions. An improvement in CoT predictions may allow researchers to predict human performance, surgical, and rehabilitation outcomes reliably using computational simulations.

scholarly journals The Impact of Odors

10.14311/322 ◽  
2002 ◽  
Vol 42 (2) ◽  
Author(s):  
M. V. Jokl
Keyword(s):  
Building Materials ◽  
Human Performance ◽  
Positive Impact ◽  
Performance Criteria ◽  
Human Organism ◽  
Sense Of Smell ◽  
Performance Loss ◽  
Exhaust Fumes ◽  
High Level ◽  
The Impact

The odor microclimate is formed by gaseous airborne components perceived either as an unpleasant smell or as a pleasant smell. Smells enter the building interior partly from outdoors (exhaust fumes - flower fragrance) and partly from indoors (building materials, smoking cigarettes - cosmetics, dishes). They affect the human organism through the olfactory center which is connected to the part of brain that is responsible for controlling people’s emotions and sexual feelings: smells therefore participate to a high level in mood formation. The sense of smell diminishes slowly in people over the age of 60, but all female age categories have a better sense of smell than males. Smell is extremely sensitive, e.g., during pregnancy, or if an illness is coming. Bad smells cause a decrease in human performance, loss of concentration, and loss of taste. Sweet smells have a positive impact on human feelings and on human performance. Criteria for odor microclimate appraisal are presented (concentration limits of CO2 , TVOC, plf, decipol, decicarbdiox, decitvoc).

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